In Delta RNAi terminal follicle cell populations are reduced. Strongly (A) and mildly (B) affected Delta RNAi ovarioles stained for f-actin with Phalloidin (red), DNA with Hoechst (blue). (C)Wildtype stalk stained for DNA with Hoechst (C’ schematic representation). Stalk cells (blue cells in C’) separate individual egg-chambers (red cells in C’) and do not contact the germ line. (A, A1) In severely affected Delta RNAi ovarioles, stalk and terminal follicle cell are absent (A1 close up of the ovariole in A; A1’ schematic representation), while lateral follicle cells are basically present. (B, B1, B2) In weak Delta RNAi phenotypes, the follicle cell epithelium appears rather normal (B1 and B2 close ups of the ovariole in B; B1’ and B2’schematic representations). Still, stalk cells are reduced (B2) in number, indicating a function for Notch-signaling in the determination of stalk cells.